Thermoplastic elastomers, which may be referred to as thermoplastic vulcanizates, are well known. They have many of the properties of elastomers, yet they are processable as thermoplastics. Thermoplastic vulcanizates are conventionally produced by dynamic vulcanization, which is a process whereby a rubber is cured or vulcanized within a blend with at least one non-vulcanizing polymer while the polymers are undergoing mixing or masticating at some elevated temperature, preferably above the melt temperature of the non-vulcanizing polymer.
For example, U.S. Pat. No. 4,130,535 discloses a thermoplastic vulcanizate comprising blends of a polyolefin resin and completely cured olefin copolymer rubber. The olefin copolymer rubber may include EPDM rubber, which is generally formed by the polymerization of monomers comprising two olefins, generally ethylene and propylene, and a lesser quantity of a non-conjugated diene monomer such as 5-ethylidene-2-norbornene. The thermoplastic matrix, however, tends to decrease resistance to compression set at lower temperatures. Some attempts have been made to improve this resistance to compression set. For example, various rubber processing oils have been added.
Because the low temperature performance of thermoplastic vulcanizates is important, there is a need in the art to improve their low temperature properties.